In many environments it is necessary to recapture oxygen from the exhaled carbon dioxide of mammals living in the environment. The most common of these situations would be a closed environment such as a submarine or a spacecraft. Generally, the reclamation process comprises passing the carbon dioxide gas through a concentrator and then directing the concentrated carbon dioxide to a carbon dioxide reduction system. Typically, the carbon dioxide reduction system results in the reaction (CO.sub.2 +4H.sub.2 .fwdarw.H.sub.2 O+CH.sub.4). The resulting water may be electrolyzed to produce hydrogen and breathing oxygen, while the methane formed may be reacted to produce carbon and hydrogen; the hydrogen being useful in the operation of fuel cell batteries on board the vessel while the carbon would be a dispensable by-product.
A typical method for the conversion of methane useful in the above-mentioned system involves passing the methane either alone or in combination with another gas into a heated reactor tube and causing the methane to pyrolytically decompose to form H.sub.2 and carbon. The carbon then remains in the reactor until such time as the build-up reduces the flow of methane into the reactor preventing the optimum operation of the reactor and necessitating its removal.
This carbon management poses a limitation on the operation of the system. U.S. Pat. No. 4,452,676 attempts to solve this problem by operating the conversion process at very high temperature, thereby creating a very dense carbon which occupies far less space in the reactor for the same quantity of methane converted, thereby allowing for longer operating cycles between cleanings.
However, the high temperatures required to operate such a reactor creates certain problems with the types of materials which may be used in the manufacture of the reactor and will also require significant energy consumption from a very limited energy source.
An alternative methane conversion system is referred to as the Bosch process, wherein the methane conversion temperatures necessary in the reactor vessel are about 700.degree. C., significantly lower than the temperatures required in the prior process described above, thereby reducing the consumption of energy required for the process. The lower operating temperatures are achieved by the introduction of an expendable iron catalyst into the reaction vessel. However, although the reaction takes place at a lower temperature, the resulting carbon has a lower packing density and therefore, requires more frequent removal than the process which produces high density carbon.
A recent study entitled Formation of Dense Carbon on Fused-Quartz Wool for Spacecraft Life Support Application discloses that the introduction of quartz wool into the reactor vessel will result in high density carbon formation and increased efficiencies for methane conversion. However, the operating temperatures were still in excess of 1000.degree. C.
Therefore, what is needed in this art is a method for converting methane gas producing hydrogen and carbon in which the operating temperatures are low, the carbon formed has a high density and the conversion efficiency remains high.